Not least, it is the ever increasing requirements for NOx and COx emissions that necessitate a very precise and highly dynamic engine management of combustion engines and their associated or downstream connected assemblies in the drive train which, moreover, may be realised by means of assemblies which can be manufactured economically and which are reliable. As an example for this, an exhaust gas recirculation scheme should be mentioned which has a very distinct influence on the NOx emission. Herein, a proportion of the exhaust gas flow is mixed with the aspirated fresh air as a function of the engine characteristics and the engine temperature and recirculated to the engine cylinders. Thereby, the oxygen content is reduced during combustion, which leads to a lower combustion temperature and results in a reduced NOx emission. Initially, only on-off valves were used for adding the exhaust gas flow to the aspirated fresh air. In the meantime, pneumatically controlled actuators are employed as well.
In order to increase the efficiency of the combustion engine, a combination of a combustion engine and an exhaust gas turbocharger may be employed. Due to the increased working pressure, the utilisation of the exhaust gas energy increases. In addition, the ratio of mechanical power loss to the overall power becomes better so that the efficiency increases. Because of the large speed range (idle up to several thousands of revolutions per minute), in particular, the full load charging pressure increases to a particularly high degree, which leads to an undesired load of the power plant. In order to limit the charging pressure, a so-called waste gate (bypass valve) may be used. An approximation of the air provided by the turbocharger to the air requirement of the combustion engine, which is dependent on the operating point, may also be achieved by a variable turbine geometry. This includes a turbine with nozzle wings at the turbine casing circumference in an annular design, which has numerous annular wings which are capable of being rotated in the casing outside the turbine wheel circumference. Another variant is a turbine with nozzle wings at the turbine casing circumference with a mechanical coupling. Here, the turbine has e. g. eight mechanically coupled wings so that they may be adjusted together and their spacing as well as the inlet cross-sectional area varied. The outlet cross-section of other variants of the turbocharger is infinitely variable by a simultaneous actuation of the wings.
For the majority of such auxiliary assemblies, stringent requirements with respect to the temperature stability of the actuator drives apply, which are located in the immediate, very hot environment of the combustion engine. An actuator drive of such an auxiliary assembly must demonstrate, for example, up to 150 to 160° C. and above as a safe operating temperature. Moreover, the stability requirements for an actuator drive of such auxiliary assemblies in an environment characterised by heavy vibrations and shocks are particularly high.
From document DE 10 2005 036 041 A1, a permanent-excited electrical machine with a stator and a rotor is known, wherein either the stator comprises a coil arrangement and the rotor is provided with permanent magnet elements, or the rotor comprises a coil arrangement and the stator is provided with permanent magnet elements. An air gap is formed between the stator and the rotor, which is defined by the permanent magnet elements and by magnetically conductive stator teeth which are aligned with these in certain positions. The coil arrangement has at least one hollow cylindrical winding.
Said stator or its parts may be built from metal sheets or sheet metal portions or formed from iron particles which are pressed and/or sintered into a corresponding shape. It is also possible to use mixed shapes from these two variants, wherein the transition areas from the radially oriented sheet metal portions to axially oriented sheet metal portions are formed from pressed or sintered iron particles.
From document DE 699 27 564 T2, a claw-pole dynamo for a bicycle is known, wherein the stator yoke is formed from pure iron magnetic steel sheets.
Document EP 0 706 461 B1 relates to an electrical drive unit for a vehicle, which is particularly suited for the travel drive of road vehicles, which consists of two electrical machines the housings of which are flanged together with the end faces in axial alignment. These electrical machines have an external rotor with a wheel body, and an internal annular stator which is formed from stator windings and stator core assemblies with an axial cylindrical recess, and which securely connected with the housing. A rotor shaft which is firmly connected with the wheel body protrudes into the axial recess of the stator. A coupling means for the output is connected with a bearing which is rotatable relative to the housing. The respective wheel body is arranged at the end face at which the two electrical machines are flanged together. The coupling means is essentially arranged within the axial recess of the stator.